1. Field of the Invention
The invention relates to an apparatus on the carousel principle for the coating of substrates, having a vacuum chamber and a revolving substrate holder disposed therein More particularly the substrate holder is one, which bears a plurality of substrate receivers at uniform intervals and in a circular array and by which a like number of substrates can, by means of a drive, be transported step-wise on a circular path from two lock stations through associated coating stations and back to the respective lock station. The step width of the drive and the angular position of each coating station are selected so that one and the same coating station is associated by the stepping movement of one particular substrate receiver with one and the same lock station.
On account of the stop made between steps to permit passage in and out of an air lock, as well as the stationary coating process, the operation of such an apparatus can be considered to be quasi-continuous.
2. Discussion of Related Art
U.S. Pat. No. 3,652,444 discloses an apparatus of the kind described above, which has three coating stations but only one lock station. The known apparatus is designed for the manufacture of semiconductors and the various coating stations in this case usually serve for the application of a whole series of coatings. The coating stations can be preceded and followed by other treatment stations in which other treatments are performed as necessary for the pretreatment and post-treatment of semiconductors. For a given arc diameter and corresponding investment costs, however, the throughput is limited, if only because the entry into and exit from the lock, including the evacuation of the lock chamber, require a certain amount of time.
There are a number of coating tasks and products in which the coating process itself and/or the pretreatments and/or after treatments require a lesser amount of time, so that the use of the known apparatus for such processes or products would be extremely uneconomical. An example of such a product is the so-called compact disk, which is to be provided on only one side with a single coating of a quickly applied, highly reflective metal such as aluminum.
Also important in the operation of such apparatus are the so-called loading stations which permit a fully automatic loading and unloading of such apparatus. Such loading stations, in connection with the corresponding magazine stations, are relatively complex and their cycle frequency cannot be fully utilized because of the relatively slow operation of the known apparatus.